The present invention relates to the preparation of metals by reduction of their salts in a process involving a chemical exchange reaction with a reducing metal for the reducible metal to be produced, in a reaction medium which ensures contact between the metals and the corresponding salts. While this process makes it possible to obtain reduced metals in either the liquid or solid state and readily separable from the reaction medium, the industrial application for which the invention is of primary interest is the production of refractory metals in the form of powder.
Among the refractory metals of the type considered, one example worthy of mention is titanium.
At the present time, the processes in most common use for the production of titanium are the Kroll process and the Hunter process which involve the use of a reducing agent consisting of magnesium or sodium metal respectively, this reducing agent being reacted with titanium chloride vapors at high temperature and in a neutral atmosphere.
These processes lead to the production of titanium in a porous form often known for this reason as titanium sponge. As a rule, however, titanium sponges cannot be used directly in this form but require subsequent purification treatments which are highly power-consuming. And if these sponges are converted to ingots, machining of ingots unfortunately results in substantial losses of material which may vary between 30% and 90% by weight, depending on the shape of the final products.
However, U.S. Pat. No. 2,839, 385 has proposed a method of reduction of titanium by magnesium in a magnesium chloride bath. But the reaction starts in this case from the dichloride TiCl.sub.2 which has to be prepared beforehand by reduction of the tetrachloride with titanium metal. Control of the intermediate production of the dichloride makes this process inconvenient and ill-adapted for use on an industrial scale.
The present invention provides a solution to these difficulties by means of a process for the production of titanium powder which can be utilized directly in powder metallurgy techniques. The advantage of this process, while particularly apparent in the case of titanium, also applies to other metals and especially tantalum which is employed in powdered form for the fabrication of capacitors as well as to niobium. Furthermore, the same process is potentially useful for producing other metals obtained in the liquid state such as magnesium.